First, the good news: The 20 inches or more of snow outside your door won’t be there forever.

The not-so-good news: Depending on how fast that snowbank melts will go a long way toward whether or not we get flooding in the next couple of weeks.

As of Sunday — and more snow is expected to fall tonight — there was at least a foot of snow on the ground in Sussex County and some areas had up to 30 inches.

The folks at the National Weather Service who keep track of such things say there’s as much as five inches of water locked up in that snow cover — that’s more than ankle-deep water to wade in everywhere there’s now snow if it were to somehow turn to liquid and stay in place.

But with the earth’s natural ripples and ridges, when the snow begins to turn liquid, it flows downhill into streams, rivers and basements.

Right now, the area’s streams and rivers are at or below normal levels for this time of year and can take quite a big of water without going over its banks.

But hydrologists — the scientists who look at the interrelation of water with the earth and atmosphere — also look at ice cover on the rivers and with the colder-than-normal temperatures, streams and rivers are ice-covered, except for areas where water is moving quickly.

“If the rivers start to rise too quick, it will break up that ice,” said Mitchell Gaines, a meteorologist with the National Weather Service’s Mount Holly station.

With that ice break-up comes the danger of ice jams, which have a damming effect and can result in flash floods upstream of the jam.

The large cakes of ice can also cause other damage. As they flow downstream on top of speeding flood waters, the cakes and slabs of ice have enough energy to uproot or knock over trees and gouge out the earth in some cases.

Sussex County sits on the border between two of the weather service’s river forecast centers. The Mid-Atlantic center looks at the streams that flow out of Sussex County and into the Delaware River, such as the Flatbrook, Pequest and Musconetcong.

The Northeast center’s region includes the Wallkill River’s drainage basin, which includes the Papakating Creek, since that river flows north and empties into the Hudson River. That area includes part or all of the towns of Wantage, Vernon, Hardyston, Frankford, Franklin, Lafayette, Byram and Sparta.

Combined maps for the two regions show the least water equivalent in the area near the Wallkill River, while the highest water content is in the highland areas of Byram and Hopatcong.

Gaines said the forecast for the storm beginning later today likely will be all snow and put another 2-4 inches of snow on what is already on the ground.

“But then we’ll start to see some melting,” he said. Wednesday and Thursday temperatures will be in the 40s with a chance of a rain shower on Thursday.

“Then we have the potential to get over 50 degrees on Friday,” he said. “It’s possible Friday will have a pretty rapid melt.”

A tempering effect to the melting, however, will be overnight temperatures dropping below the freezing point, which will slow the melt.

Early next week, the thermometer’s readings will drop back into the 30s and not get above freezing on Feb. 25, Gaines said.

The weather service’s long-range forecast through March 1 sees about average temperatures for the region with above average precipitation.

And, with each day that passes, the sun gets to stay up longer and is higher in the sky and the calendar marks one day closer to the end of winter, which won’t be forever.